Control apparatus for AC motor

Abstract

It is attained by being provided with a motor constant calculation unit for calculating electric constants of a motor, and by correcting setting values of electric constants defined on one of the axes of two orthogonal axes, by a functional expression using a state variable defined on the same axis, and by correcting them by a functional expression using a state variable defined on the other axis.

1. A control apparatus for an AC motor comprising:
 an inverter for applying pulse width modulated voltage to an AC motor, and for driving said AC motor; 
 a unit for detecting electric current of said AC motor; and 
 a controller for adjusting pulse width modulated voltage, which said inverter outputs, and for driving said AC motor; 
 wherein said controller is provided with a motor constant calculation unit for calculating electric constants of a motor, and 
 said motor constant calculation unit corrects setting values of electric constants defined on one of the axes of two orthogonal axes, by using a state variable defined on the same axis, and also corrects them by using a state variable defined on the other axis, and uses said corrected electric constants for driving control of said AC motor. 
 
     
     
       2. The control apparatus for the AC motor according to  claim 1 , wherein at least one of the correction of electric constants setting values by the state variable on said same axis, and the correction of electric constants setting values by the state variable on said other axis is corrected by a function expression using constants characterizing effects given on said electric constants by said state variable, with said state variable as a parameter. 
     
     
       3. The control apparatus for the AC motor according to  claim 2 , wherein said constants characterizing effects given on said electric constants by said state variable, with said state variable as a parameter, used in said function expression, is only one. 
     
     
       4. The control apparatus for the AC motor according to  claim 1 , wherein inductances are used as said electric constants. 
     
     
       5. The control apparatus for the AC motor according to  claim 1 , wherein back EMF constants are used as said electric constants. 
     
     
       6. The control apparatus for the AC motor according to  claim 1 , wherein electric current is used as said state variable. 
     
     
       7. The control apparatus for the AC motor according to  claim 1 , wherein when said electric constants setting values are assumed as back EMF constant Ke, and the back EMF constant at electric current with nearly zero is used as φm0, said motor constant calculation unit executes correction of Ke by q-axis electric current Iq, by using the equation of Ke(Iq)=φm0−K×Iq×Iq, wherein K is a constant. 
     
     
       8. The control apparatus for the AC motor according to  claim 1 , wherein said controller is provided with a motor control unit, and
 said motor control unit calculates voltage reference, necessary in driving of said AC motor, based on drive reference, said state variable and said corrected electric constants. 
 
     
     
       9. The control apparatus for the AC motor according to  claim 8 , wherein said motor control unit is provided with a speed calculation unit for calculating rotation speed of said AC motor, a state variable reference calculation unit for calculating state variable reference of said AC motor, and a voltage vector calculation unit, and
 said voltage vector calculation unit calculates the voltage reference from said corrected electric constants, said state variable reference and said rotation speed. 
 
     
     
       10. The control apparatus for the AC motor according to  claim 8 , wherein said drive reference is assumed as torque reference of said AC motor,
 said motor control unit is provided with a torque calculation unit, 
 said torque calculation unit calculates torque of said AC motor from said corrected electric constants and said state variable, and 
 the state variable reference is calculated so that said calculated torque comes close to said torque reference. 
 
     
     
       11. The control apparatus for the AC motor according to  claim 8 , wherein said drive reference is assumed as rotation speed reference of said AC motor,
 said controller is provided with an back EMF estimation and calculation unit, and an axis displacement calculation unit, and 
 said back EMF estimation and calculation unit and said axis displacement calculation unit estimate back EMF of said AC motor, based on said voltage reference, said state variable, said corrected electric constants and said rotation speed reference, and 
 calculate a phase thereof from said estimated back EMF, and estimates rotator position of said AC motor. 
 
     
     
       12. The control apparatus for the AC motor according to  claim 11 , wherein said back EMF estimation and axis displacement calculation unit is provided with a control axis assuming a magnetic pole axis of the inside of said AC motor; and
 an axis displacement calculation unit for calculating axis displacement between said control axis and a practical magnetic pole axis of said AC motor, and 
 calculates said axis displacement, from said state variable, said rotation speed reference, said voltage reference, and said corrected electric constants. 
 
     
     
       13. A control apparatus for an AC motor comprising:
 an inverter for applying pulse width modulated voltage to an AC motor, and for driving said AC motor; 
 a unit for detecting electric current of said AC motor; and 
 a controller for adjusting pulse width modulated voltage, which said inverter outputs, and for driving said AC motor; 
 wherein said controller is provided with a motor constant calculation unit for calculating electric constants of a motor, and 
 said motor constant calculation unit corrects setting values of electric constants defined on one of the axes of two orthogonal axes, by using a state variable defined on the same axis, and corrects them by using a state variable defined on the other axis, and uses said corrected electric constants for driving control of said AC motor, 
 and when said electric constants setting values are used as d-axis inductance Ld, and said Ld corrected by using d-axis electric current Id is used as Ld(Id), said motor constant calculation unit executes correction of Ld by q-axis electric current Iq, by using the equation of Ld(Id, Iq)=Ld(Id)−K×Iq×Iq, wherein K is a constant. 
 
     
     
       14. A control apparatus for an AC motor comprising:
 an inverter for applying pulse width modulated voltage to an AC motor, and for driving said AC motor; 
 a unit for detecting electric current of said AC motor; and 
 a controller for adjusting pulse width modulated voltage, which said inverter outputs, and for driving said AC motor; 
 wherein said controller is provided with a motor constant calculation unit for calculating electric constants of a motor, and 
 said motor constant calculation unit corrects setting values of electric constants defined on one of the axes of two orthogonal axes, by using a state variable defined on the same axis, and corrects them by using a state variable defined on the other axis, and uses said corrected electric constants for driving control of said AC motor 
 and when said electric constants setting values are used as q-axis inductance Lq, and said Lq corrected by using q-axis electric current Iq is used as Lq(Iq), said motor constant calculation unit executes correction of Lq by d-axis electric current Id, by using the equation of Lq(Id, Iq)=Lq(Iq)−K×Id, wherein K is a constant.